The present invention relates to a cutting tool assembly having replaceable indexable cutting inserts for use in rotary machining operations in general and in face milling applications in particular.
Indexable cutting inserts are normally clamped in milling cutters either directly in individual insert receiving pockets formed in the body of the milling cutter, or in cartridges retained in appropriate recesses formed in the body of the milling cutter. Cartridges can be made with an adjusting mechanism for adjusting the location of the cutting inserts. Such milling cutters requiring individually designed and produced holding members for each individual insert tend to be complex and expensive. Also, the number of inserts clamped in the milling cutter is limited by the size of the holding members.
In U.S. Pat. No. 4,522,538 a milling cutter is described that eliminates the need for producing individual holding members for each cutting insert. However, radially outward movement of the insert is prevented by the lip 26 which engages and supports a second side 51 of the insert thereby retaining the insert with the rim 22. As can clearly be seen in, e.g., FIGS. 2, 3 and 5, the rim 22 extends radially beyond the cutting inserts thereby limiting the cutting depth of the tool and the side approach to a shoulder in a workpiece.
In accordance with the present invention there is provided a cutting tool assembly rotatable about an axis of rotation A comprising:
a tool; and
a plurality of replaceable cutting inserts clamped in insert receiving pockets peripherally distributed in the tool;
the tool comprising:
a tool body; and
a crown affixed to the tool body;
the tool body has a front face divided into a peripheral portion, having a periphery, and an inner portion, the peripheral portion is frusto-conical in shape and is inwardly rearwardly directed from the periphery to the inner portion slanting at an angle xcex1;
the crown has a front face, a rear face, a peripheral side face therebetween and a plurality of peripherally distributed generally radially directed insert receiving slots opening into the front, rear and peripheral side faces;
the insert receiving pockets comprise the insert receiving slots bound axially by the peripheral portion of the tool body front face;
each insert receiving pocket has tangential, radial and axial abutment surfaces, being generally tangentially, radially and axially directed, respectively, for locating the cutting insert therein, the axial abutment surface being a portion of the peripheral portion of the front face of the tool body;
each insert receiving pocket is open in a radial direction so that at least a portion of the insert clamped therein extends radially beyond the tool.
Typically, said angle xcex1 is between 0xc2x0 to 5xc2x0.
Preferably said peripheral portion is ground.
Further preferably, said peripheral portion has equally peripherally distributed substantially radially directed recesses.
Still further preferably, said recesses open into the periphery of the peripheral portion.
Generally, each cutting insert of said plurality of replaceable cutting inserts has a geometrical shape selected from the group of octagonal, quadrangular, hexagonal and round geometrical shapes.
In accordance with the present invention, each one of said plurality of replaceable cutting inserts is clamped in the tool by means of a generally axially directed clamping screw having a front abutting portion at its front end.
Further in accordance with the present invention, the cutting insert has identical top and bottom surfaces and a side surface between the top and bottom surfaces, the cutting insert is indexable about an axis of indexing symmetry B perpendicular to the top and bottom surfaces and passing through the center thereof and is reflection symmetric about a median plane M parallel to the top and bottom surfaces, the top surface and the bottom surface meet with the side surface at top and bottom edges, respectively, at least a portion of at least one of the edges being a cutting edge having a rake surface, axial abutment surfaces directed at an angle xcex3 with respect to the median plane M extend from the top and bottom edges inwardly towards the axis B and merge at the median plane M, a continuously extending tangential abutment surface merges with the rake surface and is perpendicular to the axis B.
Preferably, said axial abutment surfaces are ground.
Typically, said tangential abutment surface has radially extending protrusions.
In accordance with a preferred embodiment, said cutting insert has clamping surfaces that extend from the tangential abutment surface in an inward direction towards the median plane M and are directed at an angle xcex2 with respect to the median plane M.
Generally, said cutting insert has a central through bore.
Typically, said cutting insert further comprises a land in the top and bottom surfaces thereof, the land merging with the cutting edges.
Preferably, the cutting edge has a relief flank in the side surface, extending from the cutting edge to the axial abutment surface.
Typically when assembled, the axial abutment surface of the cutting insert abuts against the peripheral portion of the tool body front face, at least one relief flank of the cutting insert abuts against the radial abutment surface of the crown, a tangential abutment surface of the cutting insert abuts against a tangential abutment surface of the crown and the cutting insert is clamped in the tool by means of a generally axially directed clamping screw having a front abutting portion at its front end.
In accordance with a preferred embodiment, two relief flanks of the cutting insert abut against the radial abutment surface of the crown and an axial abutment surface adjacent to the abutted axial abutment surface is located freely in a recess in the peripheral portion.
In accordance with another embodiment, the cutting insert has a top surface, a bottom surface parallel to the top surface, a side surface between the top and bottom surfaces and an axis of indexing symmetry B perpendicular to the top and bottom surfaces and passing through the center thereof, the top surface and the side surface meet at an edge, at least a part of which is a cutting edge, a rake surface in the top surface extends from the cutting edge, axial abutment surfaces directed at an angle xcex3 with respect to the top surface extend from the edge towards the bottom surface and inwardly towards the axis B, the bottom surface has a continuously extending tangential abutment surface that is perpendicular to the axis B.
Further in accordance with the present invention there is provided a cutting insert that comprises identical top and bottom surfaces and a side surface therebetween. The cutting insert is indexable about an axis of indexing symmetry B and is reflection symmetric about a median plane M parallel to the top and bottom surfaces, the top surface and the bottom surface meet with the side surface at top and bottom edges, respectively, at least a portion of at least one of the edges being a cutting edge having a rake surface, axial abutment surfaces directed at an angle xcex3 with respect to the median plane M extend from the top and bottom edges inwardly towards the axis B and merge at the median plane M, a continuously extending tangential abutment surface merges with the rake surface and is perpendicular to the axis B.
Preferably, said axial abutment surfaces are ground.
Typically, said tangential abutment surface has radially extending protrusions.
In accordance with a preferred embodiment, said cutting insert has clamping surfaces that extend from the tangential abutment surface in an inward direction towards the median plane M and are directed at an angle xcex2 with respect to the median plane M.
Generally, said cutting insert has a central through bore.
Typically, said cutting insert further comprises a land in the top surface thereof, the land merging with the cutting edges.
Also in accordance with the present invention there is provided a cutting insert having a regular octagonal shape, the cutting insert has a top surface, a bottom surface and a side surface therebetween, the cutting insert is indexable about an axis of indexing symmetry B and is reflection symmetric about a median plane M, parallel to the top and bottom surfaces,
each of the top and bottom surfaces meet with the side surface at eight cutting edges, adjacent cutting edges meet at a cutting corner, a land merges with the cutting edges and the cutting corners in each of the top and bottom surfaces, the land merges with a rake surface having edge portions adjacent cutting edges and corner portions adjacent cutting corners,
a continuously tangential abutment surface merges with the rake surface in an inward direction of the cutting insert, said tangential abutment surface is further distanced from the median plane M than the cutting edges, flat, perpendicular to the axis B and preferably ground, the tangential abutment surface has radially extending protrusions merging with each corner portion,
clamping surfaces extend from the tangential abutment surface in an inward direction towards the axis B and towards the median plane M and are directed at an angle xcex2 with respect to the median plane M,
negative relief flanks which are preferably ground merge with the cutting edges and the cutting corners in the side surface,
axial abutment surfaces preferably ground and directed at an angle xcex3 with respect to the median plane M extend inwardly from the relief flanks 80 towards the axis B and merge at the median plane M.